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Callisto
For more scientific information, visit Wikipedia, Callisto (Jupiter IV) is the second-largest moon of Jupiter, and the third-largest moon in the Solar System after Ganymede and Saturn's Titan. Callisto is a candidate moon of the reptilians' seven star colonies of the Solar System, given in Lacerta File 1999 (Question 7).Pravda Report, The Lacerta File I, pub. 2002 (Lacerta interview 1999, with commentary) Although not mentioned by name, it is likely one of the “4 moons of Jupiter and Saturn” colonies that the reptillians had colonized in the past. Specifications size comparison]] At 4,821 km in diameter, Callisto has about 99% the diameter of the planet Mercury but only about a third of its mass. It is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1,883,000 km. It is not in an orbital resonance like the three other Galilean satellites—Io, Europa, and Ganymede—and is thus not appreciably tidally heated. Callisto's rotation is tidally locked to its orbit around Jupiter, so that the same hemisphere always faces inward; Jupiter appears to stand nearly still in Callisto's sky. It is less affected by Jupiter's than the other inner satellites because of its more remote orbit, located just outside Jupiter's main radiation belt. Composition Callisto is composed of approximately equal amounts of rock and ices, with a density of about 1.83 g/cm3, the lowest density and surface gravity of Jupiter's major moons. Compounds detected spectroscopically on the surface include water ice, |accessdate=12 March 2015 }} carbon dioxide, silicates, and organic compounds. Investigation by the Galileo spacecraft revealed that Callisto may have a small silicate planetary core and possibly a of liquid water at depths greater than 100 km. Atmosphere Callisto is surrounded by an extremely thin atmosphere composed of carbon dioxide and probably molecular oxygen, as well as by a rather intense . Callisto is thought to have formed by slow accretion from the disk of the gas and dust that surrounded Jupiter after its formation. Callisto's gradual accretion and the lack of tidal heating meant that not enough heat was available for rapid differentiation. The slow convection in the interior of Callisto, which commenced soon after formation, led to partial differentiation and possibly to the formation of a subsurface ocean at a depth of 100–150 km and a small, rocky . Life on Callisto The likely presence of an ocean within Callisto leaves open the possibility that it could harbor extraterrestrial life. However, conditions are thought to be less favorable than on nearby Europa. Various space probes from Pioneers 10 and 11 to Galileo and have studied Callisto. Because of its low radiation levels, Callisto has long been considered the most suitable place for a human base for future exploration of the Jovian system. It is speculated that there could be life in Callisto's subsurface ocean. Like Europa and Ganymede, as well as Saturn's moons , Mimas, Dione and Titan, a possible subsurface ocean might be composed of salt water. It is hypothesized that s could thrive in the ocean. As with Europa and Ganymede, the idea has been raised that habitable conditions and even extraterrestrial microbial life may exist in the salty ocean under the Callistoan surface. However, the environmental conditions necessary for life appear to be less favorable on Callisto than on Europa. The principal reasons are the lack of contact with rocky material and the lower heat flux from the interior of Callisto. References The mass fraction of ices is 49–55%. }} Category:Solar System 4c